Concentrated acids or bases are commonly used as developing reagents in eluents for chromatographic separations. Ionic contaminants in the eluents can adversely affect chromatographic performance, particularly when performing ion chromatography analysis. For example, anionic contaminants such as carbonate ions from dissolved carbon dioxide gas on sodium hydroxide eluent used for anion analysis, can lead to high background noise. This problem can lead to baseline shifts during gradient analysis creating difficulties in integrating peaks leading to erroneous quantitation. One approach to addressing this problem is the use of the IONPAC® anion trap column sold by Dionex Corporation disposed between the eluent pump and a sample injector. The column is filled with anion exchange resin material for the purpose of reducing contaminants such as carbonate ions by retention on the resin. However, such columns have limited capacity and do not operate continuously, thus requiring offline regeneration such as by flowing carbonate-free hydroxide through the resin for conversion to the hydroxide form. This approach can be costly and time consuming.
Other approaches to the generation of a high purity eluent use electrolytic conversion of a purified water stream. Such approaches are described in U.S. Pat. Nos. 5,045,204, 6,225,129 and 6,036,921. However, all of these approaches require a high purity water stream.
There is a need to provide an efficient method for purifying such eluents by contaminant removal.